94 E320 transmission rebuild - PeachParts Mercedes-Benz Forum

J. M. van Swaay · #1 05-30-2010, 06:42 PM

1994 E320 (722.369 transmission)
240,000 miles
original transmission
no reverse
forward gears normal
no transmission leaks

I've been reading lots of transmission posts and rebuild manuals recently, but I have some specific questions that I really haven't found the answers to so here goes.

As usual, I'm already in way over my head, but this approach seems to facilitate lots of learning.

I've included a picture of the part that applies the clamping force to the B3 clutch pack. Note the scoring caused by intereference with the K1 clutch. The B3 friction bands are paper thin, this is obviously what allowed the B3 piston enough travel to cause the impact with the K1 clutch.

So, question 1: Does this kind of damage a require a full rebuild to insure no metal in the system? My guess is yes, but I'd like to hear from the experts.

Next, question 2: In order to remove the K2 clutch for rebuilding, must the small end of the transmission be disassembled, thereby allowing the gearset to be pulled out of the large end?

Finally, question 4: Just how much of a rebuild do the experts recommend? I'd like to be able to get 75,000 to 100,000 miles out of the rebuild.....

Thanks.

J. M. van Swaay

junqueyardjim · #2 05-30-2010, 06:52 PM

Go to a pick and pull and get one that has some life. Then with your old one out and on the shelf, take your time and try to go through it. Many have tried, some have made it work, most haven't.

J. M. van Swaay · #3 05-30-2010, 07:32 PM

Re: question 2

Answered my own question, parts blowup reveals snap ring on output shaft so yes, small end needs to be disassembled to allow removal of gearset. Missed this the first few times.......

J. M. van Swaay

ps2cho · #4 05-30-2010, 07:49 PM

If you haven't already thrown it away, tear apart the filter and see what it has picked up.

J. M. van Swaay · #5 05-30-2010, 08:04 PM

Good suggestion about cutting open the filter. Ironically, I just replaced the fluid and filter less than 100 miles ago. I did notice some grey coloring in the bottom of the pan when I cleaned it. Didn't think much of it at the time.

I'm leaning towards just replacing the B3 friction discs and all the seals that are easily accessible. Then I'll bolt it all back together and see what happens.....

J. M. van Swaay

ps2cho · #6 05-30-2010, 08:12 PM

That's pretty much what I did for mine...Just keep in mind if you do this, I would replace the fluid + filter every 5k miles for 2-3 times just to make sure there isn't anything getting stuck.

...Well...and the physical act of having to remove it again if something catastrophic does go wrong.

When putting the Torque Converter back in, do NOT make the same mistake I did and Double-Triple check it is FULLY sitting into the pump gear. It should only stick out from the housing by a few mm.
Since your TC has 230k on it, check the height of it using the FSM's specs.

J. M. van Swaay · #7 06-01-2010, 09:49 AM

Update:

Disassembly of the B3 piston revealed a torn lip seal. Picture is included with this post. I’m beginning to think that my reverse failure was the result of this lip seal failing, not worn friction discs. I would think that worn discs would result in reverse slowly getting weaker and weaker over several months. With a failed seal it seems logical to expect a more immediate failure. My symptoms were a slow advance of weak reverse, and then immediate failure.

After lots of reading and thinking, I’m still unsure just how much rebuilding to do. At a minimum, I’m planning to overhaul the B1, B2, and B3 pistons with new seals, and of course replace the B3 friction discs. I’ll also replace the front side shaft seals.

My dilemma is whether or not to open up the small end (output shaft) of the transmission. Doing so would allow shaft seal replacement and a check/rebuild of the K2 assembly. I’m less concerned about the shaft seals—If I don’t replace them and they start leaking, they can be replaced without removing the transmission.

The K1 assembly can be checked for wear as per the FSM. Haven’t done that yet but I will.

So, the real question I’m facing is how likely is it that the K2 assembly requires servicing? I’ve both heard and read that the K1 and K2 assemblies have a very long life.

Anybody have a feel for the likely condition of the K1 and especially the K2 assemblies?

Thanks for reading.

J. M. van Swaay

J. M. van Swaay · #8 06-01-2010, 11:22 AM

K1 disc play checked, value is 1.34 mm. Picture attached. FSM says max value after rebuild is 1.30mm.

Can I conclude from this that K1 is within acceptable range?

Can I reasonably expect another 75K to 100K miles from this clutch pack?

Again, thanks for reading.

J. M. van Swaay

mbdoc · #9 06-01-2010, 11:23 AM

The OLD adage is "If it ain't broke...don't fix it"

Well, with a 16 year old auto trans, that isn't true.

The least you should do is replace the B3 clutches, inspect the K1 clutch pack &
reseal the front pump. Also reseal all the outer seal rings on the trans & inspect the B2 piston clearance.

J. M. van Swaay · #10 06-03-2010, 07:13 PM

update:

Borrowed vernier caliper from a friend to measure B2 piston free play as per FSM. Free play was about 3.1 mm greater than spec. EPC shows 6 different length piston pins, shortest one is (was) currently installed. Installing 4th longest pin should bring free play back into spec.

I'm concluding from this that the B2 band is about "half" worn out. Not sure if my conclusion is correct but based on this and the K1 measurement, I plan to put it back together as previously described.

Stay tuned.....

J. M. van Swaay

J. M. van Swaay · #11 06-12-2010, 09:56 PM

Update:

Reassembled transmission, ended up replacing B3 friction discs, B1, B2, and B3 piston seals, and all o rings and gaskets on transmission case. Left small end alone--if the seals ever start leaking, they can be replaced without removing the transmission from the car. Also replaced B2 piston rod with longer one to bring B2 piston free play back to spec.

I consulted with two very experienced and knowledgeable techs, they both agreed that not opening the small end and K2 clutch pack was an acceptable risk.

Reinstalled transmission in car, everything working perfectly, solid reverse and smooth shifts in all forward gears.

Here's a few things I learned that might be helpful to someone else considering this project.

Top tranny to engine bolt: It has a bracket that makes it difficult to get a socket on it. What worked for me was to put some masking tape on the inside of the socket, then stick it on the bolt head with no driver attached. The tape prevents the socket from falling off while you feed extensions, wobble drive, and u joint up from tranny tunnel. Use one hand to feed the extensions, the other hand to guide the extension into the socket. Once I figured out this technique, the bolt was out is less than a minute.

Tranny front cover removal: The FSM describes threading two of the mounting bolts into the holes on the outside of the cover. These bolts only give you something to pull on. They DO NOT go all the way through so you can't force the cover off by torqueing these bolts. If you torque the bolts, you will crack the cover! The ATSG service document describes this mistake and subsequent fix.

B1 piston assembly: Do not disassemble. The (later style) B1 piston uses a spring washer and sliding pin to automatically adjust free play as the brake band wears. Also, do not pull it apart. If you do, you will need to remove the pin and reinstall in the max free play position. (kinda like the chain tensioner pin on the 104 engine.)

The EPC yielded an incorrect part number for the B2 piston lip seal even though I looked it up VIN specific. Apparently there was a redesign of the B2 piston guide and seal that may not be correctly coded in the EPC. (Even the MB parts guys couldn't figure it out--I came across a post on this board that had the right number)

While the tranny was out, I replaced the rear crank seal. Initially, I was hesitant to do this because the FSM describes removing the seal carrier to replace the seal. Doing this would compromise the gasket seal between the oil pan and the bottom of carrier. I ended up replacing the seal without removing the carrier. This can be done by carefully destroying the seal during removal.

All in all this was not as involved as it thought it would be. Worst part of the job was flopping around on the garage floor with a creeper to remove/install the tranny. The tranny work itself was pretty straight forward. Only tricky part is removing/installing the B1 piston because you have to overcome the spring force. I rigged up a crude installation tool, it shown in one of the atached pictures.

Here's the list of parts I replaced. Maybe it will save someone some EPC look up time. (numbers are for 722.369 transmission)

Quan Part Number Description

1 007603010112 oil pan plug seal
1 007603010100 tc plug seal
1 1262711280 front case gasket
4 1262720925 B3 friction disc
1 0169970448 bowden cable seal
1 0059978648 B1 piston o ring
1 1402770355 B1 piston teflon ring
1 0059977048 B2 piston O ring
1 1402770455 B2 piston teflon ring
1 0069977347 B2 piston lip seal
1 0109974947 torque convertor lip seal
4 007603014104 cooler line crush seals
1 0169972948 dipstick seal
1 1262720192 B3 piston seal
1 1262720092 B3 piston seal
2 1262720955 front shaft teflon rings
1 0069970147 shift shaft seal
1 1262771480 valve body gasket
1 0169971448 pump to rear housing o ring
1 1262777475 49.6 mm B2 piston pin

1 1262772973 B1 piston adjuster clip
1 1262721373 B1 circlip
1 1409931426 B1 spring washer

1 0119970647 rear crankshaft repair seal

J. M. van Swaay · #12 06-12-2010, 10:09 PM

Forgot the pictures. Here they are.

deanyel · #13 06-12-2010, 10:42 PM

Very nice thread, thanks. Where did you buy your parts? Kit or individually? About how much?

ps2cho · #14 06-15-2010, 02:40 AM

If the lip seal that was torn above, it shouldn't affect reverse operation, only potential leaks as it seals against the pump body. Although I would guess some pressure would be lost though.

Glad to hear everything worked out great for you and most importantly, functional!

J. M. van Swaay · #15 06-15-2010, 09:26 AM

I would think that the B3 piston lip seal leak would prevent pressure build up in the B3 piston when reverse gear is selected. If no pressure build up, then no clamping of the B3 friction discs. If no clamping, no reverse.

I believe the reverse failure is a sequence of events. First, the friction discs wear to quickly allowing the the B3 piston to much travel. Not only does the B3 piston impact the K1 carrier, it also allows the inside B3 piston lip seal to advance beyond the machined sliding surface. When the piston then retracts, the seal is damaged by dragging over the transition between the sliding surface and the unmachined shaft section. Leaking seal then results in no reverse.

Then again, I'm just an average DIY wrench........ I could be all wrong on this.

J. M. van Swaay